Biodegradable plastic

ABSTRACT

A biodegradable plastic added at an amount of a hydrophilic property imparting-substance providing wettability such that the contact angle of plastic surface to water is 70° or less whereby the decomposability thereof with Basidiomycetes, the cultured products thereof and/or the processed products thereof is improved. A method for decomposing plastic under the conditions with limitation to nitrogen and/or carbon in decomposing such biodegradable plastic. In accordance with the present invention, the plastic which has conventionally been decomposed with difficulty can be decomposed efficiently.

INDUSTRIAL FIELD

The present invention relates to a method for decomposing plastic and adecomposing agent therefor as well as a biodegradable plastic.

Therefore, the present invention not only makes greater contribution tothe disposal of plastic waste which is now drawing serious socialconcern, but also proposes the elucidation of the decomposing mechanismthereof and the designing of a biodegradable plastic.

BACKGROUND OF THE INVENTION

Polyolefin plastic has been considered non-biodegradable conventionally,and it has been known that only about 1% of polyethylene as a polyolefinplastic is decomposed after 10-year bacterial treatment (Journal ofApplied Polymer Science, 35, 1288-1302 (1988)).

Also, it is known a method for decomposing polyamide plastic by means ofa bacterium (Flavobacterium sp. K172) (Agr. Bio Chem., 39 (6),1219-1223(1975); Hakkoukougakukaishi, 60(5), 363-375(1982)). However,all of these conventional methods concerning polyamide plastic areclassified in the method for treating water-soluble, low-molecular nylon6 oligomer (molecular weight of about 2,000 or less). Thus,water-insoluble, high-molecular nylon (molecular weight of about 10,000or more) cannot be decomposed with these methods.

It has been known a biodegradable composition which has been modifiedfor ready biological attack by dispersing starch in a thermoplasticsynthetic resin (Japanese Patent Laid-open No. Sho 49-55740). In thebiodegradable composition, however, it is only the starch particle thatis decomposed biologically, whereas the synthetic resin cannot bedecomposed. That is, the composition is just degraded when the starchparticle is not any more decomposed, so the synthetic resin stillremains.

For the disposal of plastic waste, the rapid decomposition of plasticwaste of itself is an issue of significance. Therefore, such objectivecannot be achieved by the conventional methods, as is apparently shownin what has been described above.

Under such current technical circumstances, the present invention hasbeen performed for the objective to prevent plastic pollution. Thepresent invention has been carried out for the objective to provide amethod for efficiently decomposing plastic of itself which has neverbeen substantially decomposed by the conventional methods and to providea plastic suitable for such decomposition method.

DISCLOSURE OF THE INVENTION

The present inventors have made investigation so as to achieve theaforementioned objectives, and have thus focused their attention tobiological treatment by means of a variety of bacteria from the respectof preventing secondary pollution. However, the inventors haverecognized the need of conceptual innovation concerning microbialselection, culturing condition, treating condition and the like becausethey have not been able to achieve the primary objective. Thus, theyhave made reinvestigation.

By selecting Basidiomycetes as a microorganism, it has been found inaccordance with the present invention that enzymes generated fromBasidiomycetes cannot act on non-hydrophilic plastic but can act onplastic mixed or coated with a hydrophilic property imparting-substancewhich can then impart wettability to the plastic whereby the enzymes cansufficiently decompose the plastic of itself.

As to polyolefin plastic in particular, polyolefin plastic afterhydrophilic treatment is subjected to bacterial treatment underconditions without supplement of nitrogen source and/or carbon source asessential nutrients for bacterial growth or treatment which conditionsare totally contrary to conventional state of the art. It has been foundthat Basidiomycetes can efficiently decompose polyolefin plastic. Thus,the present invention has been achieved. In the present Specification,polyolefin plastic is often referred to as polyethylene hereinbelow.

BEST MODE OF CARRYING OUT THE INVENTION

Polyethylene, nylon, polypropylene, polyvinyl chloride, polystyrene,polyurethane, polyester and the like are included in plastic and theseare decomposable.

These types of plastic are remarkably improved of their decompositionproperty with Basidiomycetes by molding after these are mixed with asubstance imparting hydrophilic property or by coating with a substanceimparting hydrophilic property after molding. Plastic form may be eitherin film or in shape.

The substance imparting hydrophilic property may be added or coated atan amount imparting wettability such that the contact angle of theplastic surface to water is 70° or less, preferably 60° or less.

The substance imparting hydrophilic property illustratively includeshydrophilic organic substances such as starch, processed starch, cereal,mannit, lactose, dextran, cellulose, CMC, casein, higher fatty acids inlinear chain, higher alcohols in linear chain, polyethylene glycol,polypropylene glycol, Tween 80, and other various surfactants and thelike. Also, the illustrative examples thereof include hydrophilicinorganic substances such as diatomaceous earth, silica, alumina,calcium chloride, magnesium sulfate, sodium sulfate and the like.

The method for producing the biodegradable plastic of the presentinvention preferably comprises appropriately mixing the plastic inpellets with one or two or more of substances imparting hydrophilicproperty and molding the mixture following a molding method suitable foran objective molded article, but may also comprise preliminarily addinga hydrophilic substance to a plastic material during the molding processthereof and polymerizing the material. A substance imparting hydrophilicproperty may also be coated onto the surface of a molded plastic. But insuch case, it is recommended to immobilize the substance impartinghydrophilic property to effect coating.

In accordance with the present invention, wettability is essential at adegree such that the enzymes generated from Basidiomycetes may act onthe plastic. The amount of a substance to be added for impartinghydrophilic property largely varies depending on each substance, but anamount may be satisfactory if it can impart wettability such that thecontact angle of the plastic surface to water is 70° or less, preferably60° or less. The enzymes generated from Basidiomycetes can act on theplastic imparted with wettability so that various types of plastic canbe decomposed directly. The present invention further encompasses amethod for decomposing and treating the plastic treated with hydrophilicprocess so as to impart hydrophilic property or plastic originallyhaving hydrophilic property, by means of Basidiomycetes, the culturedproducts thereof and/or the processed products thereof. Furthermore, theplastic having hydrophilic property may be decomposed withBasidiomycetes, the cultured products thereof and/or the processedproducts thereof under the conditions with limitation to nitrogen and/orcarbon.

Basidiomycetes may be from natural origin, but such Basidiomycetes isnot so abundant to show satisfactory decomposing activity. A decomposingagent containing preliminarily cultured Basidiomycetes in preparationmay be sprayed on.

In accordance with the present invention, Basidiomycetes, wood rotBasidiomycetes in particular, may be used frequently, but white rotBasidiomycetes, namely lignin decomposing bacterium, is specificallyused advantageously.

Such white rot Basidiomycetes illustratively includes the fungi from thefollowing genera; Coriolus versicolor, IFO 7043, etc.; Phanerochaetechrysosporium, ACTT 34541, etc.; Trametes dickinsii, IFO 6488, etc.;Polyporus mikadoi, IFO 6517, etc.; Stereum frustulosum, IFO 4932, etc.;Ganoderma applanatum, IFO 6499, etc.; Lenzites betulina, IFO 8714, etc.;Fomes fomentarius, IFO 30371, etc.; Porodisculus pendulus, IFO 4967,etc.; Lentinus edodes, IFO 31336, L. lepideus, IFO 7043, etc.; Serpulalacrymans, IFO 8697, etc.; and the like.

In addition to those described above, strain NK-1148 (FERM BP-1859) andstrain Porodisculus pendulus (strain NK-729W; FERM BP-1860) maysatisfactorily be used. The strain NK-1148 is a microorganism isolatedby the present inventors and is deposited as FERM BP-1589 in the PatentMicroorganism Depository, Fermentation Research Institute, Agency ofIndustrial Science and Technology, at 1-3, Higashi 1-chome, Tsukuba-shi,Ibaraki-ken, 305, Japan (original deposition date; May 23, 1987). Thedetailed mycological characteristics thereof are disclosed in JapanesePatent Publication No. Hei 3-32997.

The decomposing agent containing Basidiomycetes is generally produced byinoculating and culturing various Basidiomycetes in wood powder and thenpreparing the powder into particles, but various liquid culturedproducts or various solid cultured products may be used appropriately.It is also recommended to use the products from the culture ofBasidiomycetes under the conditions with limitation to nitrogen and/orcarbon.

Only if the Basidiomycetes agent of the present invention is sprayedonto the plastic waste added with a hydrophilic propertyimparting-substance whereby the plastic is rendered decomposable withBasidiomycetes, the cultured products thereof and/or the processedproducts thereof, the plastic is decomposed with Basidiomycetes, thecultured products thereof and/or the processed products thereof, therebydisposing the waste for a short period of time.

The present invention further comprises decomposing polyolefin plasticwith one or more of Basidiomycetes described above, and then, it is moreefficient to treat the plastic with hydrophilic process or under theconditions with limitation to nitrogen and/or carbon.

More specifically, when polyolefin plastic is made to contact toBasidiomycetes at an optimum temperature, for example, 15° to 35° C.,preferably in the state with limitation to nitrogen and/or carbon,polyolefin plastic can be decomposed extremely efficiently at about 5 to30 days.

In such case, it is important to limit nitrogen and/or carbon in spiteof microbial treatment. Nitrogen and/or carbon should be rendered asless as possible. Preferably, nitrogen and/or carbon is not containedtherein. From industrial respect, however, the nitrogen concentrationshould be 0.1 g/l or less. If the concentration is rendered 0.05 g/l,better results can be obtained. The carbon concentration should be 1.0g/l, and more preferably, the concentration should be 0.2 g/l. With nospecific limitation to the nutrients other than nitrogen and carbon,individual components routinely employed for the growth ofBasidiomycetes may appropriately be used. If the aforementionedconditions regarding nitrogen and/or carbon are satisfied, the intendedobjective can be attained in accordance with the present invention.Therefore, polyolefin plastic can be decomposed in the state whereinnitrogen sources and carbon sources are completely eliminated, forexample, by adding polyolefin plastic and Basidiomycetes to water forincubation.

In accordance with the present invention, Basidiomycetes is employed,and in addition to the Basidiomycetes of itself, the cultured productsthereof and/or the processed products thereof may be employed as well.By the cultured products thereof are broadly meant the mixture of themycelia obtained by culturing the Basidiomycetes with the culture broth.In accordance with the present invention, the mycelia in the form ofsuch as wet cake separated from the culture, the residue thereof and theculture broth obtained by completely removing the mycelia , may be alsoemployed. Furthermore, the processed products thereof mean all of thoseobtained by concentrating, drying or diluting those described above. Byusing the cultured products and processed products of Basidiomycetescultured with limitation to nitrogen and/or carbon, polyolefin plasticshould satisfactorily be decomposed.

In subjecting polyolefin plastic to decomposition process according tothe present invention, polyolefin plastic is preferably subjected tohydrophilic process so as to readily contact polyolefin plastic to themicroorganisms, enzymes generated therefrom or the like. As thehydrophilic process of polyolefin plastic, use may be made of a methodcomprising coating and/or mixing surfactants routinely employed, amethod comprising coating and/or mixing inorganic matters or organicmatters and the like. As a specifically preferable method therefor, amethod is recommended, comprising adding a substance impartinghydrophilic property to the surface or inside of plastic to beprocessed, thereby providing wettability such that the contact angle ofthe plastic surface to water should be 70° or less, preferably 60° orless. Furthermore, such polyolefin plastic is more preferably powderedor made porous. In accordance with the present invention, any polyolefinplastic can be decomposed other than high-pressure polyethylene, low-and medium-pressure polyethylene, and other various polypropylene. It isneedless to say that the mixtures thereof may be biodegradable.

The present invention will now be explained in details with reference toexamples, but the present invention is not limited to the followingexamples. It is to be understood that any modification of the presentinvention may be encompassed within the technical scope of the presentinvention, unless departing from the spirit what has been describedhereinabove and what will be described hereinafter.

EXAMPLE 1

Placing hydrophilic polyethylene films (HYPORE PE-1100; manufactured byAsahi Kasei, Co. Ltd.) onto a solid medium (KH₂ PO₄ : 1.0 g, NaH₂ PO₄ :0.2 g, MgSO₅ ·7H₂ O: 0.1 g, ZnSO₄ ·7H₂ O: 0.01 mg, CuSO₄ ·5H₂ O: 0.02mg, glucose: 20 g, agar: 30 g, water: 1 liter), the inoculation ofindividual microorganisms (white rot Basidiomycetes; Phanerochaetechrysosporium ATCC 34541, Coriolus versicolor IFO 7043, NK-1148 FERMBP-1859; brown rot Basidiomycetes; Lentinus lepideus IFO 7043, Serpulalacrymans IFO EPRI 6352, incomplete fungi; Aspergillus niger IFO 6341,Penicillium citrinum IFO 6352, bacteria; Bacillus subtilis IFO 3134,Pseudomonas paucimobillis SYK-6) was done followed by stationary cultureat 20° to 28° C. for 20 days. After incubation, the polyethylene filmswere suspended in water. Biodegradability was evaluated by observationof the suspension state. Furthermore, the polyethylene films highlydecomposed by observation were analyzed by GPC (Column KS-80Mmanufactured by Showa Denko, Co. Ltd., elution solution; TCB, flow rate;1 ml/min, temperature; 135° C., detector; RI). The biodegradability wasassessed through the modification of the average molecular weight. Theresults are shown in the following Table 1.

                  TABLE 1                                                         ______________________________________                                        Polyethylene decomposition activity of each microorganism                                              Weight    Number                                                              average   average                                                    Dispersi-                                                                              molecular molecular                                  Bacterial species                                                                             bility   weight    weight                                     ______________________________________                                        Lumber rot Basidiomycetes                                                     White rot Basidiomycetes                                                      P. chrysosporium                                                                              ++                                                            C. versicolor   +                                                             NK-1148         +++      10,000    2,000                                      Brown rot Basidiomycetes                                                      L. lepideus     +                                                             S. lacrymans    +                                                             Incomplete fungi                                                              Aspergillus niger                                                                             -                                                             Penicillium citrinum                                                                          -                                                             Bacteria                                                                      Bacillus subtilis                                                                             -                                                             Ps. paucimobillis                                                                             -                                                             ______________________________________                                         Note-1; Dispersibility                                                        High: ++                                                                      Medium: +                                                                     Low:                                                                          Non dispersible:                                                              Note2; Control (without microbial treatment)                                  Weight average molecular weight 125,000                                       Number average molecular weight 29,000                                   

As is apparently shown in Table 1, it was confirmed that wood rotBasidiomycetes can decompose polyethylene film. Such films were highlydecomposed, specifically when strain NK-1148 was used. GPC analysisshowed that polyethylene of a weight average molecular weight of125,000, which has absolutely never been decomposed conventionally, wasdecomposed into a weight average molecular weight of 10,300.

EXAMPLE 2

Using the white rot Basidiomycetes (NK-1148) and following the treatingconditions as in Example 1, stationery culture was done on a solidmedium with a different nitrogen concentration (the same mediumcomposition as in Example 1, except that the nitrogen concentration wasadjusted to 0 g/l, 0.05 g/l, 0.10 g/l and 0.15 g/l via ammonium sulfateaddition) for assessing the decomposability following Example 1. Theresults are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Effects of nitrogen concentration in the medium                               on polyethylene decomposition                                                 N concentration                                                                              Dispersibility                                                 ______________________________________                                        0.15 g/l       -                                                              0.10 g/l       +                                                              0.05 g/l       ++                                                              0.0 g/l       +++                                                            ______________________________________                                         Note-1; Dispersibility                                                        High: ++                                                                      Medium: +                                                                     Low:                                                                          Non dispersible:                                                         

EXAMPLE 3

Using the white rot Basidiomycetes (NK-1148) and following the treatingconditions as in Example 1, stationery culture was done on a solidmedium with a different carbon concentration (the same mediumcomposition as in Example 1, except that the carbon concentration wasadjusted to 0 g/l, 0.2 g/l, 0.4 g/l and 8.0 g/l via glucose addition;and nitrogen concentration was adjusted to 0.15 g/l via 0.58 g ofammonium sulfate addition) for assessing the decomposability followingExample 1. The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                        Effect of carbon concentration in the medium                                  on polyethylene decomposition                                                 Carbon concentration                                                                           Dispersibility                                               ______________________________________                                        8.0 g/l          -                                                            0.4 g/l          +                                                            0.2 g/l          ++                                                           0.0 g/l          +++                                                          ______________________________________                                         Note-1; Dispersibility                                                        High: ++                                                                      Medium: +                                                                     Low:                                                                          Non dispersible:                                                         

EXAMPLE 4

Using the white rot Basidiomycetes (NK-1148) and following the treatingconditions as in Example 1, stationery culture was done on two types ofsolid media, namely a solid medium without nitrogen and carbon sources(the same medium composition as in Example 1 except that glucose wasadjusted to 0 g) and a solid medium produced by removing all of thenutrients from the medium of Example 1 (30 g of agar and 1 liter ofwater), for assessing the decomposability following Example 1. Theresults are shown in table 4.

                  TABLE 4                                                         ______________________________________                                        Effects of medium nitrogen and carbon concentrations                          on polyethylene decomposition                                                 Carbon     Nitrogen                                                           concentration                                                                            concentration                                                      (g/l)                   Dispersibility                                        ______________________________________                                        0.0        0.0              +++                                               0.0        0.0              +++                                                          (All of nutrients removed)                                         0.0        0.15             +++                                               8.0        0.0              +++                                               8.0        0.15             -                                                 ______________________________________                                         Note-1; Dispersibility                                                        High: ++                                                                      Medium: +                                                                     Low:                                                                          Non dispersible:                                                         

EXAMPLE 5

In the solid medium of the nitrogen concentration at which the maximumdecomposition activity in Example 2 was exhibited (at 0 g/l ammoniumsulfate and at the other conditions as the same in Example 1), theeffect of the hydrophilic process of polyethylene film was examined, byusing white rot Basidiomycetes (NK-1148). As samples, use was made ofhydrophobic polyethylene film (HYPORE PE-2100 manufactured by AsahiKasei, Co. Ltd.) and the polyethylene film treated with a surfactant(the hydrophobic film after immersion in an aqueous 0.1% Tween 80solution for 24 hours) for imparting hydrophilic property. Thedecomposability was examined by GPC as in Example 1. The results areshown in Table 5.

                  TABLE 5                                                         ______________________________________                                        Effects of the hydrophilic process of polyethylene                            on polyethylene decomposition                                                 Hydrophilic Weight average                                                                             Number average                                       process     molecular weight                                                                           molecular weight                                     ______________________________________                                        No          144,000      29,000                                               Yes          24,500       3,100                                               ______________________________________                                         Note-1; Control (without fungal treatment)                                    Weight average molecular weight 145,000                                       Number average molecular weight 29,000                                   

EXAMPLE 6

After mixing 10 parts by weight of nylon 66 in pellets (manufactured byAldrich) and one part each of various additives for impartinghydrophilic property, i.e. polyethylene glycol (manufactured by WAKOCHEMICALS), polypropylene glycol (manufactured by WAKO CHEMICALS), Tween80 (manufactured by KISHIDA, Co. Ltd.) and silica (MIZUCASIL P-700manufactured by MIZUSAWA INDUSTRIAL COMPANY, Co. Ltd.), the resultingmixture was dissolved in 100 parts by weight of hexafluoroisopropanol tomake a cast solution. By using a spreader for thin-layer chromatography,the cast solution was uniformly cast on glass surface. Then,hexafluoroisopropanol was removed under reduced pressure to produce anylon 66 film imparted with hydrophilic property. Also, nylon 66 filmswithout various additives mixed (with no hydrophilic property imparted)were prepared by the same method. The contact angles of these variousfilms to water were measured by liquid-drop method (Polymer Society,Committee of Polymer and Water: Polymer and Water (Saiwai Press)).

These various films were placed on a solid medium (KH₂ PO₄ : 1.0 g, NaH₂PO₄ : 0.2 g, MgSO₄ ·7H₂ O: 0.1 g, ZnSO₄ ·7H₂ O: 0.01 mg, CuSO₄ ·5H₂ O:0.02 mg, glucose: 20 g, agar: 30 g, water: 1 liter), followed by theinoculation of white rot Basidiomycetes (NK-1148) for stationery cultureat 28° C. for 10 days. After the culture, the nylon 66 films weremeasured of their molecular weight and assessed of theirbiodegradability.

The molecular weight distribution was analyzed by high-temperature GPC(150-C manufactured by Waters, Co. Ltd.). The analytical conditions wereas follows; columns; Microstylagel HT-linear and Ultrastylagel 500,manufactured by Waters, Co. Ltd., elution solution; m-cresol, flow rate;1 ml/min temperature; 100° C., detector; RI. The average molecularweights of the samples after such fungal treatment are shown in Table 6.

                  TABLE 6                                                         ______________________________________                                        Presence and types                                                                          Weight average                                                                             Number average                                     of additives  molecular weight                                                                           molecular weight                                   ______________________________________                                        No addition   151,000      25,000                                             (without hydrophilic                                                          property imparted)                                                            Addition                                                                      (with hydrophilic                                                             property imparted)                                                            Polyethylene glycol                                                                         50,000       5,000                                              Polypropylene glycol                                                                        63,000       7,000                                              Tween 80      54,000       6,000                                              Silica        66,000       8,000                                              ______________________________________                                         Note; Control (without fungal treatment)                                      Weight average molecular weight 187,000                                       Number average molecular weight 43,000                                   

EXAMPLE 7

Except for the use of polyethylene with hydrophilic property impartedthrough silica addition (PE-1100 manufactured by Asahi Kasei, Co. Ltd.)and polyethylene without hydrophilic property imparted (PE-2100manufactured by Asahi Kasei, Co. Ltd.) and that the incubation periodwas set at 20 days, the same biodegradability test as in Example 6 wasundertaken.

The molecular weight distribution was analyzed by high-temperature GPC(150-C manufactured by Waters, Co. Ltd.). The analytical conditions wereas follows; columns; Microstylagel HT-linear and Ultrastylagel 500,manufactured by Waters, Co. Ltd., elution solution; m-cresol, flow rate;1 ml/min, temperature; 135° C., detector; RI. The average molecularweights of the samples after such fungal treatment are shown in Table 7.

                  TABLE 7                                                         ______________________________________                                                      Weight average                                                                              Number average                                    Samples       molecular weight                                                                            molecular weight                                  ______________________________________                                        Polyethylene without                                                          silica added                                                                  Before fungal treatment                                                                     145,000       29,000                                            After fungal treatment                                                                      144,000       29,000                                            Polyethylene with                                                             silica added                                                                  Before fungal treatment                                                                     125,000       29,000                                            After fungal treatment                                                                       10,000        2,000                                            ______________________________________                                    

INDUSTRIAL APPLICABILITY

In accordance with the present invention, plastic can be decomposedefficiently. Also, such highly biodegradable plastic can be provided.Additionally, no secondary pollution is induced. Thus, the presentinvention makes great contribution to the disposal of plastic wastewhich is now drawing serious social concern.

What is claimed is:
 1. A biodegradable plastic produced by adding asubstance imparting hydrophilic property to a plastic material,characterized in that the plastic is decomposed by Basidiomycetes, thecultured products thereof and/or the processed products thereof.
 2. Abiodegradable plastic according to claim 1, wherein the substanceimparting hydrophilic property is a hydrophilic organic substance.
 3. Abiodegradable plastic according to claim 1, wherein the substanceimparting hydrophilic property is a hydrophilic inorganic substance. 4.A biodegradable plastic according to claim 1, having wettability suchthat the contact angle thereof to water is 70° or less.
 5. Abiodegradable plastic according to any one of claims 1 to 4, wherein theplastic material is polyolefin plastic.
 6. A biodegradable plasticaccording to any one of claims 1 to 4, wherein the plastic material ispolyamide plastic.
 7. A method for decomposing plastic whereinpolyolefin plastic is decomposed with Basidiomycetes, the culturedproducts thereof and/or the processed products thereof.
 8. A method fordecomposing plastic according to claim 7, wherein the polyolefin plasticis decomposed under conditions such that nitrogen concentration is notmore than 0.1 g/l and carbon concentration is not more than 1.0 g/l . 9.A method for decomposing plastic comprising adding a substance impartinghydrophilic property to a plastic material and decomposing the materialwith Basidiomycetes, the cultured products thereof and/or the processedproducts thereof.
 10. A method for decomposing plastic according toclaim 9, wherein the plastic material is polyolefin plastic.
 11. Amethod for decomposing plastic according to claim 10, wherein thepolyolefin plastic is decomposed under conditions such that nitrogenconcentration is not more than 0.1 g/l and carbon concentration is notmore than 1.0 g/l.
 12. A method for decomposing plastic according toclaim 10, comprising preparing the polyolefin plastic into powder orporous film and decomposing the plastic with Basidiomycetes, thecultured products thereof and/or the processed products thereof.
 13. Amethod for decomposing plastic according to any one of claims 9, 10 or12, wherein the Basidiomycetes is wood rot Basidiomycetes.
 14. A methodfor decomposing plastic according to claim 13, wherein said wood rodBasidiomycetes is white rot Basidiomycetes.
 15. A method for decomposingplastic according to claim 14, wherein the white rot Basidiomycetes isstrain NK-1148.
 16. A method for decomposing plastic according to claim14, wherein the white rot Basidiomycetes is Porodisculus pendulusNK-729W strain.
 17. A plastic decomposing agent containingBasidiomycetes, the cultured products thereof and/or the processedproducts thereof.
 18. A plastic decomposing agent according to claim 17,wherein the Basidiomycetes is strain NK-1148.
 19. A method fordecomposing plastic according to claim 17, wherein the Basidiomycetes isPorodisculus pendulus NK-729W strain.